1. Field of the Invention
The present invention generally relates to mechanical impact fuzing of rifle fired munitions and more specifically, to such fuzing of shells with diameters 40 mm and under as used in anti-aircraft defense, air-to-air, air-to-groiund, and ground-to-ground systems
2. Description of Prior Art
A mechanical impact fuze has been developed for 20 mm fuzes which meets current safety and arming requirements for the U.S. military, but leaves considerable room for improvement. Current requirements include the detection of two independent firing signatures, traditionally set back and spin, before completely arming the fuze. Two other characteristics that have been desired, but not satisfactorily implemented are second impact detonation and an arming delay, not only to prevent premature firing in the barrel, but to protect friendly forces close to or in front of the weapon. Second impact detonation has meant the ability to poke through the skin of an aircraft and explode them inside on impact with a wing spar or other structural member.
The current fuzes for 20 mm ammunition use out-of-line detonators and fire on the first impact. An earlier model of this type of fuze had provisions for second impact detonation by virtue of adjusted detonator sensitivity to shock, but was found to be unreliable. To provide additional arming delay a number of techniques have been investigated. These include time escapement mechanisms, as first used in watches and clocks; slow burning pyrotechnic trains and fluid dashpots using gases and liquids. The dashpots have shown the most promise, but there are still problems with temperature, viscosity, aging and costs. Another desirable characteristic is the ability to detect and fire on a grazing impact.